What does everyone do these days to protect agaist rust.

I have a mint 1999 Chevy Silverado. It has 450000 kms on it and runs like it brand new. The one problem is that I cant seem to keep the rust from stopping underneath. Iv tried painting undercoating ext. but it still seems to show through after 3 months. Any ideas to keep my truck rust free for many more years to come. In better words how to stop rust from getting any worse once its already started.

Attached Files:

Nothing that I know of! I've lost more vehicles due to rust and corrosion! The county I live in don't use salt in the winter, but where I work does, so I cant get away from it! Rust eats up everything unless you wanna wash your truck every week!

Once corrosion has started the only way to stop/prevent further damage is to completely remove the existing corrosion, then apply a paint or coating system that revents futher moisture intrusion and corrosion.
Treating the raw metal with a conversion coating prior to using a top or protective coating goes a long ways towards halting damage.